摘要
铁电材料的力电耦合特性以及在纳米尺度的快速失效导致其剪切过程很难研究,而材料的脆性也限制了这些材料在铁电器件中的潜在应用.在这项工作中,我们使用分子动力学方法模拟了剪切和畴演变的动态过程,揭示了这些畴结构如何影响材料的力电性能.在原子尺度上,一个明显的极化旋涡状的畴结构出现在剪切带的尖端,两侧分别有180°和90°的畴壁.由应变梯度引起的挠曲电效应导致了这些复杂的畴结构.施加外部电场阻碍畴的翻转,并通过减少积累的能量减少了失配应变区域,加速了剪切过程.结果表明极化旋涡畴阻碍了剪切破坏过程,这启示我们可以通过设计畴结构来增韧铁电材料.
The shear failure of ferroelectric material is hard to investigate because of the electromechanical properties of the material and its high speed at the nanoscale.The brittleness of the material also limits the potential applications of these materials in ferroelectric devices.In this work,we use atomic simulations to investigate simultaneously the dynamic process of shearing and domain evolution to clarify how these affect the dielectric properties of the material.On the atomic scale,an apparent polarization vortex-like domain structure appears at the tip of the shear band with 180°and 90°domain walls on each side.These complex domain structures are attributed to the flexoelectric effect induced by a strain gradient.An external electric field is introduced to hinder domain switching and prevent misfit strain regions,which accelerates the shearing process by reducing accumulated energy.The results reveal that polarization vortices impede shear failure and the mechanism allows us to toughen ferroelectric materials by manipulating the domain structure.
作者
陈玉峻
王鸿宇
楼旭辉
郭浩
李晓雁
王清远
范海冬
田晓宝
Yujun Chen;Hongyu Wang;Xuhui Lou;Hao Guo;Xiaoyan Li;Qingyuan Wang;Haidong Fan;Xiaobao Tian(MOE Key Laboratory of Deep Earth Science and Engineering,College of Architecture and Environment,Sichuan University,Chengdu,610065,China;Department of Mechanics,Sichuan University,Chengdu,610065,China;School of Urban Construction,Material Simulation and Computing Laboratory,Hebei Normal University of Science&Technology,Qinhuangdao,066004,China;Center for Advanced Mechanics and Materials,Applied Mechanics Laboratory,Department of Engineering Mechanics,Tsinghua University,Beijing,100084,China)
基金
supported by the National Defense Science&Technology Innovation Zone Project,the Natural Science Foundation of China(Grant No.12072213)
the National Science and Technology Major Project(Grant No.J2019-Ⅲ-0010-0054)
the National Numerical Windtunnel(Grant No.NNW2019-JT01-023)
We thank Zhenhuan Li(Huazhong University of Science and Technology)and Jiangyu Li(Southern University of Science and Technology)for the useful discussion.
